simple_completableFuture.java

public Future<String> calculateAsync() throws InterruptedException {
    CompletableFuture<String> completableFuture = new CompletableFuture<>();
 
    Executors.newCachedThreadPool().submit(() -> {
        Thread.sleep(500);
        completableFuture.complete("Hello");
        return null;
    });
 
    return completableFuture;
}